Process of electrolessly depositing metal coatings having metallic particles dispersed therethrough

ABSTRACT

THERE ARE DISCLOSED HEREIN PROCESSES FOR ELECTROLESS METALLIZING WORKPIECES TO PROVIDE THEREON AN ELECTROLESS PLATING METAL COATING INCORPORATING THEREIN METALLIC PARTICLES, WORKPIECES PRODUCED BY SUCH PROCESSES AND PLATING BATHS WHICH ARE USEFUL IN THE PRACTICE OF SUCH PROCESSES AND FOR PRODCING SUCH WORKPIECES. THESE PROCESSES GENERALLY COMPRISE CONTACTING THE WORKPIECES WITH AN ELECTROLESS METALLIZING BATH CONSISTING OF AN AQUEOUS SOLUTION OF AN ELECTROLESS METAL PLATING SALT AND A CHEMICAL REDUCING AGENT THEREFOR AND A QUANITY OF METALLIC PARTICLES, WHEREIN SAID PARTICLES ARE ESSENTIALLY INSOLUBLE IN SAID BATH AND INERT AND NON-CATALYTIC AND NON-POISONOUS WITH RESPECT THERETO AND NON-DISPLACING WITH RESPECT TO THE ELECTROLESS PLATING METAL JONS IN SAID BATH, THE PARTICLES BEING PRESENT IN SAID BATH EXPRESSED AS FREE METAL, AND MAINTAINING THE PARTICLES IN SUSPENSIN THROUGHOUT THE BATH DURING THE METALLIZING OF THE WORKPIECE; THE METALLIZING BATH MAY CONTAIN NICKEL IONS OR COBALT IONS OR MIXTURES THEREOF AS A SOURCE OF METAL AND MAY CONTAIN HYPROPHOSPHITE ANION OR AN ALKYLBORAZANE OR A BOROHYDRIDE AS THE REDUCING AGENT, OR MAY CONTAIN COPPER IONS AS A SOURCE OF METAL WITH FORMALDEHYDE AS THE REDUCING AGENT; THE METALLIC PARTICLES ARE SELECTED FROM CHROMIUM, MOLYBDENUM, TUNGSTEN, BORON, TITANIUM, VANDAIUM, ZIRCONIUM, NIOBIUM, TANTALUM AND ALLOYS THEREOF; THE METALIC PARTICLES HAVE DIMENSIONS IN THE RANGE FROM ABOUT 0.1 MICRON TO 50 MICRONS; THESE METALLIC PARTICLES MAY BE MAINTAINED IN SUSPENSION IN THE BATH BY MECHANICAL AGITATION, BY PASSING THE BATH INCLUDING THE PARTICLES OVER THE WORKPIECE, BY PASSING STREAMS OF MINUTE BUBBLES OR GAS THROUGH THE BATH, BY AGITATION AND MOVEMENT OF THE WORKPIECE WITHIN THE BATH, OR BY SLOWLY ROTATING THE WORKPIECE IN CONJUNCTION WITH THE RAPID CIRCULATION OF THE BATH; ADDITIONALLY, THE ELECTROLESS PLATING METAL COATING HAVING THE METALLIC PARTICLES INCORPORATED THEREIN MAY BE HEAT-TREATED BY HEATING TO A TEMPERATURE IN THE RANGE FROM ABOUT 200* C. TO ABOUT 1,300*C. FOR AT LEAST ONE-QUARTER HOUR TO BOND SAID ELECTROLESS METAL COATING AND SAID METALLIC PARTICLES AT THE INTERFACES THEREOF.

V/CKERS PYRAMID NUMBER I V P N I Feb. 9, 1971 K. PARKER 3,562,000 PROCESS OF ELECTROLESSLY DEPOSITING, METAL COATINGS HAVING METALLIC PARTICLES DISPERSED THERIITHROUGH Filed on. 25, 1968 FIGJ ELECTROLESS NICKELB TUNGSTEN ELECTROLESS NICKEL ELECTROLESS NICKEL 8 CHROMIUM TEMPERA TURE C" IVPN.)

I r ELEC TROLESS NICKEL a CHROMIUM a I MOL YBDENUM VICKERS PYRAMID NUMBER -ELECTROLE$$ NICKEL a v HAYNES N0.l57

I I I I ELEC TROLESS NICKEL ELECTROLESS NICKEL 8 HAYNES N06 TEMPERA TURE C IN VEN TOR KONRAD PARKER p. 2; [5M (2 7' M r Q I ATTYS.

United States Patent 3,562,000 PROCESS OF ELECTROLESSLY DEPOSITING METAL COATINGS HAVING METALLIC PARTICLES DISPERSED THERETHROUGH Konrad lParker, Park Ridge, 10., assignor to General American Transportation Corporation, Chicago, 11]., a corporation of New York Filed Oct. 25, 1968, Ser. No. 770,573 Int. Cl. C23c 3/02 U.S. Cl. 117-130 36 Claims ABSTRACT OF THE DISCLOSURE There are disclosed herein processes for electroless metallizing workpieces to provide thereon an electroless plating metal coating incorporating therein metallic particles, workpieces produced by such processes and plating baths which are useful in the practice of such processes and for producing such workpieces. These processes generally comprise contacting the workpieces with an electroless metallizing bath consisting of an aqueous solution of an electroless metal plating salt and a chemical reducing agent therefor and a quantity of metallic particles, wherein said particles are essentially insoluble in said bath and inert and non-catalytic and non-poisonous with respect thereto and non-displacing with respect to the electroless plating metal ions in said bath, the particles bemg present in said bath in an amount by weight no greater than about ten times the weight of the electroless plating metal in said bath expressed as free metal, and maintaining the particles in suspension throughout the bath during the metallizing of the workpiece; the metallizing bath may contain nickel ions or cobalt ions or mixtures thereof as a source of metal and may contain hypophosphite anion or an alkylborazane or a borohydride as the reducing agent, or may contain copper ions as a source of metal with formaldehyde as the reducing agent; the metallic particles are selected from chromium, molybdenum, tungsten, boron, titanium, vanadium, zirconium, niobium, tantalum and alloys thereof; the metallic particles have dimensions in the range from about 0.1 micron to 50 microns; these metallic particles may be maintained in suspension in the bath by mechanical agitation, by passing the bath including the particles over the workpiece, by passing streams of minute bubbles of gas through the bath, by agitation and movement of the workpiece within the bath, or by slowly rotating the workpiece in conjunction with the rapid circulation of the bath; additionally, the electroless plating metal coating having the metallic particles incorporated therein may be heat-treated by heating to a temperature in the range from about 200 C. to about 1,300 C. for at least one-quarter hour to bond said electroless metal coating and said metallic particles at the interfaces thereof.

The present invention is directed to processes for electroless metallizing workpieces wherein the resultant electroless plating metal coating has incorporated therein metallic particles, workpieces produced by such processes and to plating baths useful in carrying out processes of this invention in producing such workpieces.

It is a principal object of the present invention to provide a process for electroless metallizing a body to provide thereon an electroless plating metal coating incorporating therein metallic particles so as to provide such body with a coating which is resistant to corrosion such as by acids and which has improved hardness and wear characteristics, as well as other improved physical, chemical and electrochemical characteristics.

Generally, the process comprises contacting the body with an electroless metallizing bath consisting essentially of an aqueous solution of an electroless plating metal salt and a chemical reducing agent therefor and a quantity of metallic particles, wherein the particles are essentially insoluble in the bath and inert and non-catalytic and nonpoisonous with respect thereto and non-displacing with respect to the electroless plating metal ions in the bath, the particles being present in the bath in an amount by weight no greater than about ten times the weight of the electroless plating metal in the bath expressed as free metal, and maintaining the metallic particles in suspension throughout the bath during the metallizing of the body, thereby to produce on the surface of the body a coating of the electroless plating metal having the metallic particles uniformly dispersed therethrough.

Another object of the invention is to provide a process of electroless metallizing of the type set forth wherein the metallic particles have dimensions in the range from about 0.1 micron to about 50 microns, the particles being maintained in suspension in the bath by mechanical agitation of the bath or by passing the bath including the particles across the body, or by passing streams of minute bubbles of gases through the bath, or by agitation of the body within the bath, or by slowly rotating the body in conjunction with the rapid circulation of the bath.

A further object of this invention is to provide a process of electroless metallizing of the type set forth wherein the resulting electroless plating metal coating incorporating metallic particles therein has a thickness in the range from about 1 micron to about 250 microns.

Still another object of the invention is to provide a process of electroless metallizing of the type set forth which further includes the step of heating the coating in a vacuum, or in an inert or reducing atmosphere to an elevated temperature for a sufficient period of time to bond or alloy the electroless plating metal coating thereof, the heat-treatment generally consisting of heating to a temperature in the range from about 200 to about 1,300 C. for at least one-quarter hour.

Still another object of the invention is to provide a process of the type set forth for applying to bodies the electroless plating metal coatings incorporating therein metallic particles formed of a metal selected from the group consisting of chromium, molybdenum, tungsten, boron, titanium, vanadium, zirconium, hafnium, niobium, tantalum and alloys thereof.

A further object of the invention is to provide a process of the type set forth which is particularly suited for applying electroless plating metal coatings to bodies formed of a material selected from iron, aluminum, magnesium, copper, nickel, beryllium, titanium, and alloys thereof Another object of the invention is to provide an article of manufacture comprising a workpiece having an electroless plating metal coating incorporating metallic particles thereon made by the processes set forth herein.

A still further object of the invention is to provide an article of manufacture comprising a workpiece having an electroless plating metal coating thereon made in accordance with the processes of the present invention including the heat-treatment of the coating, wherein the electroless plating metal is an electroless nickel and the metallic particles are selected from chromium and its alloys.

Still another object of this invention is to provide a bath for the chemical plating of the catalytic material with an electroless plating metal coating incorporating therein metallic particles, the bath comprising an aqueous solution of an electroless metal plating salt and a chemical reducing agent therefor and a quantity of metallic particles, wherein the particles are essentially insoluble in the bath and inert and non'catalytic and non-poisonous with respect thereto and non-displacing with respect to ice the electroless plating metal ions in the bath, the particles being present in said bath in an amount by weight no greater than about ten times the weight of the electroless plating metal in the bath expressed as free metal.

Further features of the invention pertain to the particular arrangement of the steps of the processes and the compositions of the bath used therein and of the electroless plating metal coatings produced thereby, whereby the above outlined and additional operating features thereof are attained.

The invention both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification and to the several illustrative examples and the appended drawings wherein:

FIG. 1 shows a series of curves illustrating the hardness-temperature relationship of several electroless nickel coatings including various metallic particles as compared to electroless nickel coatings lacking any metallic particles; and

FIG. 2 shows a further series of curves illustrating the hardness-temperature relationship of electroless nickel.

coatings including still other types of metallic particles as compared with electroless nickel coatings lacking any metallic particles.

In accordance with the present invention, there is provided a workpiece or body having an outer surface that is to carry the desired electroless plating metal coating, the outer surface typically being one that will be subject to contact with corrosive fluids such as acids and the like or that will be subject to sliding or rubbing contact with another surface, whereby it will be subjected to substantial wearing and bearing pressures. First, the surface of the workpiece is cleaned using any one of several well known cleaning methods appropriate to the metal substrate, after which the workpiece is contacted with an electroless metallizing bath containing a quantity of metallic particles, the particles being essentially insoluble in the plating bath and inert and non-catalytic and non-poisonous with respect thereto and non-displacing with respect to the electroless plating metal ions in the bath, the particles being present in the bath in an amount by weight no greater than about ten times the Weight of the electroless plating metal in the bath expressed as free metal.

A suitable bath for the practice of this process is, for example, a conventional chemical nickel plating bath of the nickel cation-hypophosphite anion type in which the metallic particles are suspended. During the plating process, the metallic particles are maintained in suspension throughout the bath by mechanical agitation or other such means, whereby after a suitable period of time there is produced on the surface of the workpiece a coating of the electroless plating metal, such as nickel for example, having uniformly dispersed therethrough a quantity of the metallic particles. Thereafter, the workpiece may be subjected to a heat-treatment step in order to alloy or bond the electroless plating metal and the metallic parrides at the interfaces thereof thereby imparting desirable characteristics to the coating.

The coatings provided in accordance with the processes set forth herein lend to the workpiece various desirable properties; for example, some of these coatings will increase the corrosion resistance of the workpiece as against such corrosive fluids as acids and the like and against oxidation at high temperatures; additionally, other of these coatings provide a surface which is intrinsically harder than the surface of the workpiece itself, thereby increasing the resistance to wear and abrasion. Other desirable properties may similarly be achieved by employing such coatings on the surface of the workpiece as will be more fully explained hereinafter.

While the processes of the present invention are fundamentally independent of the composition of the workpiece, ordinarily the workpiece is formed of an industrial metal such as steel or iron for example, although the workpiece Cir may be formed of other metallic and non-metallic materials. Where non-metallic materials are utilized as workpieces, these workpieces must first be subjected to a pretreatment step in order to prepare the surface so that it may subsequently receive the electroless metallized coating that is inherently produced in the metallizing process described herein. When the metallizing metal is nickel the pretreatment on plastics and non-conducting surfaces may be that as disclosed in U.S. Pat. No. 2,690,401, granted on Sept. 8, 1954 to Gregoire Gutzeit, Wm. J. Crehan and Abraham Krieg, and in U.S. Pat. No. 2,690,402 granted on Sept. 28, 1954 to Wm. J. Crehan.

The processes of the present invention are particularly beneficial in providing electroless plating metal coatings on workpieces formed of such materials as aluminum, magnesium, copper, nickel, titanium, or beryllium, whereby desirable surface properties may be imparted to the workpiece without the necessity of a high heat-treatment step.

It will be understood that a large number of metallizing processes of the electroless type may be utilized including electroless nickel processes, electroless cobalt processes and electroless copper processes. The invention is of particular applicability, however, in the case of electroless nickel processes, specifically those using hypophosphite anions as the electroless reducing agent. Furthermore, the electroless metallizing process in the case of electroless nickel is independent of the particular composition of the nickel plating bath of the nickel cation-hypophosite anion type that is employed in the chemical nickel plating step, whereby a wide variety of these conventional chemical nickel plating baths may be employed.

The plating bath disclosed in U.S. Pat. No. 2,822,294, granted on Feb. 4, 1958 to Gregoire Gutzeit, Paul Talmey and Warren G. Lee is recommended due to its simplicity and economy. More particularly, this plating bath is of the nickel cation-hypophosphite anion type, also containing lactic anion and propionic anion, and having a pH in the acid range 3.5 to 6.0. A typical example of this chemical nickel plating bath useful in the present invention is as follows:

EXAMPLE 1 NiSO .6H O: 0.08 mole/liter NaH PO .H O: 0.23 mole/liter Lactic acid: 0.30 mole/liter Propionic acid: 0.03 mole/liter Lead ion: 1 part per million pH: 4.6

A quantity of the above plating bath was placed in a plating vessel provided with a magentic stirrer and a hot plate for agitating and heating the bath, respectively. Thereafter, there was added chromium powder (325 mesh) in an amount equal to 0.5% by weight of the solids in the plating bath, the chromium powder being maintained in suspension by the stirrer. A clean steel workpiece was then placed in the plating bath while the temperature of the plating bath was maintained in the general range from about C. to C, and while the chromium particles were maintained in agitated suspension. After about an hour, there was present on the exposed surfaces of the workpiece an electroless plating metal coating of approximately 12.5 microns in thickness comprising electroless nickel and a quantity of chromium par ticles uniformly dispersed therethrough. The coating that is inherently produced by this particular plating bath essentially comprises by weight about 77% nickel, 8% phosphorus and about 15% chromium.

The surface of the coated workpiece was a dull light gray in color having a slightly rough surface. This coating as plated had a hardness in the nickel-phosphoruschromium alloy area of 610 V.P.N. (Vickers Pyramid Number) and a Table Wear Index (TWI) value of 4.6. The Table Wear Index is defined as the loss of weight in milligrams per 1000 revolutions of two CS-lO rubber wheels under a 1000 grams load, a TWI of 5 representing a loss in thickness of about 0.25 micron of coating. By contrast, an electroless nickel coating on a test panel made in accordance with Example 1 but without the addition of the chromium particles thereto has a V.P.N. value of 560 as plated, and a TWI value of 15, whereby it is apparent that the coating of the present invention incorporating therein chromium particles improves the hardness and wear resistance of the coating by a factor of 3 In the chemical nickel plating bath of Example 1, the absolute concentration of hypophosphite in the bath expressed in mole/liter may vary within the range from about 10.15 to about 1.20 and the ratio between the nickel cations and hypophosphite anions in the bath expressed in molar concentration may vary within the range from about 0.20 to'about 1.60. The lactic acid serves as a complexing agent and may be derived from lactic acid or salts thereof. The absolute concentration of lactic ions in the bath expressed in mole/liter being within the range from about 0.25 to about 0.60. The bath also includes an exalting additive, namely, the propionic acid, which has a concentration in the bath expressed in mole/liter in the range from about 0.025 to about 0.60. Other exalting additives may be used in place of the propionic acid, the eXalting additive being selected from the group consisting of simple short chain saturated aliphatic monocarboxylic acids, dicarboxylic acids including 3 to 5 carbon atoms, dibasic acids and amino acids and salts thereof. Details of the composition of such a bath and the method of using same are set forth in the aforementioned US. Patent No. 2,822,294 and the disclosure thereof is incorporated herein by reference.

The chromium particles useful in the process of EX- ample 1 may have a particle size in the range from about 0.1 micron to about 50 microns, in order to obtain good suspension of the particles in the plating bath and in order to obtain uniform distribution of said particles in the coating. Smaller particles inhibit the plating action due to close packing, while larger particles cannot easily be dispersed and suspended in the plating bath. The concentration of the chromium particles in the plating bath should not exceed above ten times the weight of the nickel metal present in the bath expressed as nickel metal, although smaller concentrations of the chromium particles may be utilized, it being clear that the volume of chromium particles in the coating will be a function of the concentration and the size of the chromium particles in the plating bath as Well as the effectiveness of the dispersion thereof. In Example 1, the chromium particles comprise about 20% by volume of the metal coating al- I though it will be understood that the volume of the chromium particles may vary from as little as 5% to as much as 65% of the volume of the coating.

The thickness of the coating is primarily dependent upon the plating time and in Example 1 after about 1 hour the thickness was found to be 12.5 microns. Other i thicknesses of the coating may be provided by varying the plating time, temperature and pH and the coating may have a thickness in the range from about 1 micron to about 250 microns.

The electroless metallizing processes disclosed herein, such as the process described in Example 1, may be carried out in a continuous system where it is desirable to practice this invention on a commercial scale. Generally, such a system involves the periodic or continuous regeneration of the plating bath by the addition thereto of appropriate ingredients for the purpose of maintaining substantially constant the composition of the bath. Furthermore, it is necessary to maintain substantially constant the pH of the bath by the periodic or continuous addition of either a soluble alkali hydroxide or a soluble alkaline salt, or by the addition of a buffer salt or a combination of buffers. The system is made continuous by providing a regular plating chamber maintained at the plating temperature in which the plating operation is carried out and to which is attached a relatively large reservoir containing a much larger proportion of the bath solution maintained at a lower temperature to avoid thermal decomposition. The bath solution is circulated at a low rate from the reservoir to the plating chamber after being preheated, and back again to the reservoir during which time lating may continue. When it is necessary to replenish exhausted ingredients and adjust the pH, the necessary ingredients may be added to the reservoir while the sys tem is in operation without disrupting the plating operation, and further without causing random chemical reduction of the nickel ions in the bath with resultant de composition of the bath. The precise means for carrying out such a continuous system and methods whereby such a system may be practiced is disclosed in US. Pat. No. 2,658,839 granted Nov. l0, 1953 to Paul Talmey and William J. Crehan, the disclosure of that patent being incorporated herein by reference.

Electroless metallizing baths such as disclosed herein and specifically disclosed in Example 1, have the tendency to slow down rapidly with time due to the fact that the anions of the metal plating salt dissolved in the plating bath combine with the hydrogen cations to form an acid, which, in turn, lowers the pH of the bath, and the reducing power of the hypophosphite anions is decreased as the pH is lowered reducing the efiiciency of the bath. In addition, there occurs a random chemical reduction of the nickel cations in the plating bath causing the formation of a black precipitate which results in decomposition of the plating bath. Although various exaltants and buffers have been devised to overcome this problem, decomposition still occurs especially in a continuous system such as described above. This problem may be overcome by the addition of trace amounts of water soluble additives of dipolar molecular characteristics. The anion and cation of the dipolar molecule dissociate and the anion forms a water insoluble product with the various suspensoids in the bath forming a product which is hydrophobic or Water-repellent. Sulfhydric compounds perform this function since these compounds have at least one functional group with an affinity for metals and a hydrophobic radical characterized by forming oriented waterrepellent coatings on metal surface. Hence, a trace amount of sulfide ions having a concentration in the range of from 1 to about 10 parts per million stabilizes electroless metallizing plating baths of the character described herein, the preferred range being from about 1 to about 5 parts per million. At a concentration beyond 10 parts per million, however, these elements are catalytic poisons interfering with the metallic reduction reaction. Examples of elements which will perform quite well as stabilizers when added to the bath include lead, tellurium, tin, and cadmium. Other elements which will perform satisfactorily include copper, bismuth, selenium, tungsten, thorium, titanium, zinc, manganese and rhenium. These stabilizers may conveniently be provided in the form of metallic salts which dissociate when added to the bath. Organic thio-compounds which are soluble under plating conditions and which hydrolyze with respect to the sulphur content at a rate to maintain a sulfide ion concentration as indicated may similarly be utilized. The lead content of the nickel plating bath of Example 1 therefore, performs the function of stabilizing the bath during the plating operation. Other types of stabilizers may be advantageously utilized in connection with the present invention, suitable such stabilizer being disclosed in US. Pat. No. 2,762,723 granted Sept. 11, 1965 to Paul Talmey and Gregoire Gutzeit, the disclosure of that patent being incorporated herein by reference.

Summarizing with respect to Example 1 above, there is described a process of electroless plating of a nickelalloy coating on a steel workpiece, the coating containing chromium particles uniformly dispersed therethrough. The expression electroless plating" as used herein refers to the plating of metal coatings without the application of an external electrical current by a chemical reduction of the electroless plating metal utilizing a chemical reducing agent for the metal, thereby to accomplish a process of electroless metallizing.

Alkaline nickel plating baths may be utilized advantageously in the present invention, and particularly when coating certain plastics and certain metals such as aluminum and magnesium, examples of suitable alkaline baths being set forth in US. Pat. No. 3,211,578 granted on October 12, 1965 to Gregoire Gutzeit, the disclosure thereof being incorporated herein by reference.

The metallic particles utilized in the processes of the present invention must be essentially insoluble in the plating bath, that is such particles must have a very low solubility therein on the order of no more than about 0.01 mole/liter. In addition, these metallic particles must be inert and non-catalytic and non-poisonous with respect to the bath and non-displacing with respect to the electroless plating metal ions in said bath. For example, some metal powders are catalysts for the nickel reduction reaction and will therefore cause spontaneous decomposition of the bath. Such metallic particles as iron, nickel, cobalt, palladium, platinum, ruthenium, rhodium, silver and gold are catalysts for the nickel reduction reaction and will therefore result in spontaneous decomposition of the bath when utilized as the metallic particles in said bath. Other metals such as antimony, bismuth, copper, cadmium, indium, lead, tin, mercury and zinc are catalytic poisons of the nickel reduction reaction and will therefore prevent plating when present in more than trace amounts. Various electropositive metals such as beryllium, aluminum, manganese and magnesium will cause a displacement reaction with the electroless plating metal ions in solution, especially nickel ions. These metallic particles become nickel coated and then act as catalytic nuclei for a spontaneous decomposition of the bath.

Those metals mentioned above which will cause a displacement reaction to occur with the electroless plating metal ions, such as aluminum, may be utilized as the material of the workpiece to be plated. In this instance a displacement reaction occurs on the surface thereof almost instantaneously upon immersion in the bath such that the workpiece receives a nickel coating thereon which may then be electroless plated in accordance with the processes of this invention.

The metallic particles may be maintained in suspension throughout the bath by the mechanical agitation of the bath with the particles therein such as by the use of a magnetic or electric stirrer as illustrated in Example 1. Another method for maintaining the metallic particles in suspension consists of pumping a mixture of the plating solution including the metallic particles through the plating vessel, the bottom of the plating vessel being dishshaped and symmetrical, whereby a uniform stream of the plating bath with the metallic particles suspended therein is passed or flooded across the surfaces of the workpiece being coated.

Another method for maintaining the metallic particles in suspension is to provide a symmetrical plating bath having dispersed in the bottom thereof a spider including a number of very small gas orifices therein. In this manner very fine air bubbles may be introduced into the plat ing bath through the orifices, the air bubbles serving to hold metallic particles in suspension throughout the plating solution. In addition to air, other gases such as nitrogen or any one of the noble gases may be utilized. Ultrasonic energy may also be used for dispersion.

A further method of maintaining the particles in suspension is to agitate and move the workpiece Within the plating solution thereby causing currents in the plating solution which tend to hold the particles in suspension.

Yet another method for maintaining the metallic particles in suspension consists of slowly agitating the workpiece while at the same time rapidly circulating the plat- 8 ing solution throughout the bath such as by using a pump or the like thereby causing the bath solution with the metallic particles to pass across or flood the surface of the workpiece while the workpiece produces mild agitation.

The coating produced by the process of Example 1 is particularly useful when applied to workpieces having surfaces that are to be employed in sliding application, such as slide bearings, motor housings, shafts and the like. In addition, especially where the coating is subsequently heat-treated as will be illustrated hereinafter the coating of Example I greatly increases the corrosion resistance of workpiece against corrosion due to acids and other such fluids. Hence workpieces having such corrosion-resistant coatings on their surfaces are particularly useful as liners for vessels which are to carry acidic solutions and the like. It will be understood, however, that the incorporation of metallic particles in the electroless deposited plating metal coating affects other properties of the coating in addition to the hardness and corrosion resistance thereof. Other physical, chemical and electrochemical properties affected include the coeflicient of friction, the oxidation stability of the coating, the reflectivity and/or gloss thereof and other such properties.

FIG. 1 of the drawings shows a series of curves illustrating the hardness-temperature relationship involved in the heat treatment of various nickel coatings including metallic particles as contrasted with heat-treated nickel coatings lacking any metallic particles dispersed therein. Each curve was constructed by computing the V.P.N. hardness value after heat treatment for one hour at various temperatures within the range of C. to about 700 C. The curve representing the hardness-temperature relationship with respect to the electroless nickel coating including chromium particles has a hardness of about 630 V.P.N. at 100 C. which increases rapidly to a peak of 1330 V.P.N. at 300 C. as contrasted to a coating of electroless nickel lacking any metallic particles which has a hardness of 560 V.P.N. at 100 C. and a maximum hardness of 1020 V.P.N. at a temperature of 400 C.

Where the heat-treatment of the coating including the metallic particles is carried out in the temperature range of about 600 C. to about 1300 C., the metallic particles are not only bonded to the electroless plating metal by Wetting the surface thereof, but the particles are alloyed with the electroless plating metal at least at the interfaces thereof. Heat treatment in the range of from about 1,200 C. to about 1,300 C. for a period of from about one hour to about sixteen hours results in homogenization of the structure and solutionizing of the alloyed particles. The heat-treatment step is carried out in an oven under vacuum conditions, or in an inert or reducing atmosphere, such as an atmosphere consisting of argon or hydrogen gas. The vacuum condition, or the inert or reducing atmospheres are employed during the heating step in order to prevent surface oxidation.

The resistance of the coating of Example 1 to corrosion due to acids is also particularly manifested when the coating is heat-treated following immersion in the electroless metallizing bath. The following is an example of the heat-treatment of the novel coating of Example 1.

EXAMPLE 2 The steel workpiece having a coating thereon produced as in Example 1 was gradually heated in an oven to 600 C. for a period of one hour. From test coupons exposed to a solution of 10% sulfuric acid at room temperature for 17 hours, the corrosion rate was computed to be 22 mdd. whereas the corrosion rate of a coating produced in accordance with Example 1 but without the addition of the chromium particles was computed to be 91 mdd. The corrosion rate is derived by calculating the weight loss of the coupons expressed in terms of milligrams per square decimeter per day (mdd.). The corrosion rate may similarly be computed by calculating the weight loss when exposed to a solution of 10% hydrochloric acid at 9 180 F. for from 1 to 3 hours. The weight loss was 33% lower for the coating produced in Example 2 than for a nickel coating without metallic particles disposed there- Utilizing the bath described in Example 1, other metallic particles may similarly be utilized in producing coatings having the desirous physical and chemical properties indicated.

EXAMPLE 3 To an electroless metallizing bath consisting of the components described in Example 1, was added 1% by Weight of the solids in the bath of molybdenum powder having an average particle size of 3 microns. A steel workpiece was then placed in the plating bath while the molybdenum particles were maintained in agitated suspension throughout the plating bath, and while the temperature of the bath was maintained in the range of from 93 C. to 98 C. After an hour, there was present on the surface of the workpiece an electroless metal coating comprising electroless nickel and a quantity of molybdenum particles uniformly dispersed therethrough said coating having a thickness of 15 microns. The coating that is inherently produced by this plating bath comprises by weight about 57.5% nickel, phosphorus and 35% molybdenum.

The surface of the coated workpiece was a dull light gray in appearance having a slightly rough surface, the coating possessing the valuable properties described with respect to the coating of Example 1.

The hardness and corrosion resistance of the electroless nickel coating incorporating therein molybdenum particles as described in Example 3 are improved by heattreatment of the coating following the plating thereof.

EXAMPLE 4 A test coupon having the coating thereon produced in Example 3 was gradually heated in an oven at about 600 C. for a period of one hour. The coupons were immersed in sulfuric acid for 17 hours and at the end of that time the corrosion rate was computed and found to be 25 mdd. as compared with a value of 133 for a coating produced in accordance with Example 3 but without the molybdenum particles and similarly heated to 600 for one hour.

The process of Example 1 is similarly useful for producing an electroless nickel coating having both chromium and molybdenum particles uniformly dispersed therethrough.

EXAMPLE 5 To an electroless metallizing bath consisting of the components described in Example 1, was added 1.0% by weight of the solids in the bath of a mixture consisting of chromium particles and molybdenum particles in equal amounts by weight. After one hour of plating, a coating having a thickness of 12.5 microns was deposited on the surface of the steel workpiece. The corrosion rate when calculated from immersion in a 10% solution of hydrochloric acid at 180 F. for between 1 and 3 hours was calculated to be 2500 mdd. for the coating as produced in Example 5 as compared with a value of 7900 mdd. for the coating produced by the process of Example 1 but without any metallic particles incorporated therein.

The coating of Example 5 may further be improved in terms of its hardness and corrosion resistance by heattreating said coating as follows:

EXAMPLE 6 The workpiece with the coating of Example 5 thereon was heat-treated in an inert atmosphere oven to 600 C. for a period of 1 hour. The hardness of said coating was found to have a value of 1160 V.P.N. and a corrosion rate of 70 mdd. when calculated from a 10% solution of sulfuric acid at room temperature for 17 hours. By contrast a coating produced in accordance with Example 10 1 but without the incorporation of any metallic particles has a hardness of 650 V.P.N. and a corrosion rate in 10% sulfuric acid at room temperature of 91 mdd. after heattreatment at 600 for 1 hour.

As shown in FIG. 2, the hardness of the electroless nickel coating including chromium and molybdenum particles does not surpass the hardness of the electroless nickel coating until heat-treated to a temperature of about 500 C., the peak hardness being 1160 V.P.N. at about 550 C.

Other metallic particles may similarly be used in carrying out processes of the present invention.

EXAMPLE 7 The plating bath and process of Example 1 was repeated but there was substituted 0.5% by weight of the solids in the bath of tungsten powder with an average particle size of 1 micron in place of the chromium powder utilized in Example 1. A dull coating was deposited on the steel workpiece having a thickness of 12.5 microns after 1 hour of coating time, the coating having a composition consisting of 62.6% nickel, 5.6% phosphorus and 30.2% tungsten.

Heat-treatment of the coating produced in accordance with Example 7 imparts further desirable properties to said coating.

EXAMPLE 8 The workpiece with the coating of Example 7 thereon was further processed and heat-treated by heating same in an oven to 600 C. for a period of 1 hour. The corrosion rate of the resulting coating was found to be 66 mdd. in a 10% sulfuric acid solution after 17 hours at room temperature as contrasted with a value of 91 mdd.

' for a coating lacking any metallic particles and heattreated to 600 C. for 1 hour.

As shown in FIG. 1, the hardness of the electroless nickel coating including tungsten does not surpass that of the electroless nickel coating lacking any particles, but does increase by heat-treatment of the coating, the peak hardness being about 819 V.P.N. after heating to 400 C. as compared to about 1,000 V.P.N. for the plain electroless nickel coating.

EXAMPLE 9 The plating bath and the coating process of Example 1 were duplicated except that 0.5 by weight of the sol ids in the bath of boron powder (1 to 2 microns) was substituted for the chromium powder utilized in Example 1. After one hour of plating, a coating having a thickness of 2.5 microns was deposited on the surface of the workpieces, the coating having a hardness of 605 V.P.N. as plated, as contrasted with a value of 560 V.P.N. for a nickel coating lacking any metallic particles dispersed therein,

EXAMPLE 10 The workpiece with the coating of Example 9 was further processed and heat-treated by heating the same in an oven to 500 C. for a period of one hour. The hardness of the coating after heat-treatment was found to have a value of 1047 V.P.N. as contrasted with a value of 825 V.P.N. for a nickel coating lacking any metallic particles dispersed therein similarly heat-treated.

EXAMPLE 11 The plating bath and the coating process of Example 1 were duplicated except that 0.5 by weight of the solids in the bath of titanium powder was substituted for the chromium powder utilized in Example 1. After 1 hour of plating a coating having a thickness of 17.5 microns was deposited on the surface of the workpiece, having similarly good properties with respect to hardness and corrosion resistance as the other coatings produced by the foregoing examples.

1 1 EXAMPLE 12 The plating bath and the coating process of Example 1 were duplicated except that 0.5 by weight of the sol ids in the bath of vanadium powder was substituted for the chromium powder utilized in Example 1. After 1 hour of plating, a coating having a thickness of about 2.5 microns 'was then deposited on the surface of the workpiece having similarly good properties with respect to hardness and corrosion resistance as the other coatings produced in the foregoing examples.

The plating bath in the coating process of Example 1 may be duplicated, substituting for the chromium powder utilized in Example 1, 0.5 by weight of the solids in the bath of either zirconium, hafnium, or tantalum powder, as illustrated in Examples 11 and 12 with titanium and vanadium powders respectively. Coatings produced with an electroless nickel incorporating therein either zirconium, hafnium and tantalum or alloys thereof exhibit similarly useful characteristics with respect to hardness, corrosion resistance and the like, and which may also be heat-treated as described in Example 2 above.

EXAMPLE 13 The plating bath and coating process of Example 1 were again duplicated except that in place of the chromium powder utilized in Example 1, there is substituted a mixture including 1.5% chromium, 1.5 molybdenum and 0.4% tungsten. All of said percentages are based upon the weight of the solids in the plating bath. A steel workpiece was then immersed in the plating bath for a period of 1 hour and following deposition of the coating therein, the workpiece was heat-treated by heating said workpiece to a temperature of 600 C. for 1 hour. The corrosion rate of the workpiece was computed to be 28 mdd. in a solution of sulfuric acid as compared to 91 mdd. for a workpiece having a nickel coating but with no metallic particles dispersed therein.

EXAMPLE 14 The procedure of Example 1 was repeated substituting in the place of chromium powder, a mixture including 1.5 chromium, 1.5 molybdenum, 0.4% tungsten and 0.1% vanadium, all of the percentages being by weight of the solids in the plating bath. A steel workpiece was immersed in the plating bath and the coating continued for a period of 1 hour resulting in a coating having a composition consisting of 59.5% nickel, 5.7% phosphorus and 33.0% of the metallic particles based upon the weight of the coating. The physical and chemical properties of the coating produced compared favorably with coatings produced in accordance with the foregoing examples.

EXAMPLE 15 The plating bath and process of Example 1 was again duplicated except that the plating bath had dispersed therein 1% by weight of the solids in the bath of Haynes Stellite No. 157 powder, which consists of 21% chromium, 0.07% carbon, 1.6% silicon, 2.40% boron, 4.50% tungsten and the balance being cobalt. A steel workpiece was immersed in a plating bath for a period of 1 hour producing an electroless nickel coating on the steel workpiece having the metallic particles dispersed therethrough. The coating, as plated, had a hardness of 580 V.P.N. which was improved after heating the workpiece including the coating to a temperature of 400 C. for 1 hour to a value of 1209 V.P.N. By contrast a coating produced in accordance with Example 1 but lacking any metallic particles dispersed in the nickel coating had a hardness of 1020 V.P.N. after being heat-treated at a temperature of 400 C. for 1 hour.

As shown in FIG. 2, the electroless nickel coating including Haynes Stellite No. 157 has a greater hardness than electroless nickel coatings lacking any metallic particles after heat treatment throughout the temperature range of from about 100 C. to about 650 C.

EXAMPLE 16 The plating bath and coating process of Example 1 were duplicated employing 0.5% 'by weight of the solids in the bath of Haynes Stellite No. 6 powder in place of the chromium powder utilized in Example 1. Haynes Stellite No. 6 has the approximate chemical composition of 28.0% chromium, 1.0% carbon, 1.0% silicon, 1.0% manganese, 3.0% iron, 3.0% nickel, 4.0% tungsten with the balance being cobalt. There resulted from 1 hour of plating, a coating having a thickness of about 17.5 microns and composed of nickel, 9% phosphorous and 6% of the alloy metallic particles. The workpiece as plated had a hardness of 570 V.P.N. as compared to 560 V.P.N. for a nickel coating lacking any metallic particles dispersed therein.

EXAMPLE 17 The workpiece with the coating of Example 16 was further processed and heat-treated by heating in an oven to a temperature of 600 for 1 hour thereby providing a coating having a corrosion rate of 45 mdd. when calculated from a 10% solution of sulfuric acid as contrasted with 91 mdd. for a nickel coating lacking any metallic particles dispersed therein after a similar heat treatment.

As shown in FIG. 2, the hardness of the electroless nickel coating including Haynes Stellite No. 6 is similarly improved after heat-treatment thereof, having a peak hardness of about 775 V.P.N. at 500 C. as contrasted with a hardness of only 570' V.P.N. at 100 C.

Alkaline nickel pating baths may similarly be utilized advantageously in the present invention, and particularly when coating such metals as aluminum, magnesium and others. The following example illustrates the use of an alkaline nickel bath in practicing the process of this invention.

EXAMPLE 18 To one liter of deionized water was added the followmg:

Grams Nickel sulfate 33 Sodium hypophosphite 10 Amonium citrate 100 Chromium powder (400 mesh) 10 The pH was adjusted to 8.5-9 with ammonia, and the solution was heated with agitation to C. A clean aluminum workpiece was immersed in the bath and there resulted a coating consisting of electroless nickel having chromium particles dispersed therethrough having a thickness of 8.33 microns after 1 hour of plating time. The coating was dull in appearance and had excellent adhesion to the substrate and further, possessed the advantageous properties as described with respect to the coating of Example 1.

EXAMPLE 19 An acetate nickel bath is utilized incorporating the following components.

To 600 milliliters of deionized Water was added the following:

Grams Nickel chloride 21.0 Sodium hypophosphite 25.0 Sodium acetate 10.0

The volume was brought to one liter with deionized water and 10 grams of chromium powder was added and the bath heated with stirring to 95 C. A clean aluminum workpiece was immersed in the bath and there resulted after 1 hour of plating, a coating thereon having the thickness of about 20 microns. This coating possessed similar desirable properties and characteristics as de 13 scribed above with respect to the coating produced by the process of Example 1.

The foregoing Examples 1 through 19 illustrate various embodiments in the processes of this invention wherein the electroless metal plating salt employed in the electroless metallizing bath is a nickel salt. However, similarly good results are obtained in producing coatings with the desirable properties and characteristics described with respect to the nickel coatings when other electroless metal plating salts are utilized. The following example illustrates the use of cobalt as the electroless plating metal and the coating obtained thereby.

EXAMPLE 20 To 2,000 milliliters of deionized water is added the following:

Grams Cobalt chloride 105 Sodium citrate 185 Ammonium sulfate 210 Sodium hypophosphite 75 The pH was adjusted to 8.7:05 with ammonia and the volume brought to 3,000 milliliters with deionized water. To this bath was added 1% by weight of the solids in the bath of Haynes Stellite No. 6 powder and the plating bath was then heated with stirring to 90 C. A clean aluminum workpiece was immersed in the bath and there resulted a coating having a thickness of 3.65 microns after 1 hour of plating time. The coated aluminum workpiece was dull gray in appearance and the coating had excellent adhesion to the substrate, such that when the workpiece was bent through 180 on a inch mandrel, the coating did not separate from the substrate.

Example 20 illustrates the use of a cobalt salt for plating an aluminum workpiece. It is to be understood that any other suitable workpiece may be employed in an electroless cobalt bath. The following example describes the coating of a steel workpiece in such an electroless cobalt bath.

EXAMPLE 21 An electroless bath was formulated having the following ingredients:

Grams per liter Cobalt chloride 50 Rochelle salt 375 Ammonium chloride 100 Sodium hypophosphite 35 The pH of the bath was adjusted to 9.0 with ammonia and the temperature of the bath maintained at about 98 C. There was then added grams of chromium powder which was maintained in suspension by stirring the bath with a mechanical stirrer. A clean steel workpiece was immersed in the bath and after 1 hour of plating there was produced a coating having a thickness of 7.25 microns, being slightly rough and dull in appearance. The workpiece with the coating thereon possessed similarly desirable properties and characteristics as described for the coating produced by the process of Example 20.

Two electroless plating metals may be co-deposited from an electroless plating bath as is known in the art and such plating solutions are useful in carrying out the process of the instant invention, the following being an example thereof:

EXAMPLE 22 An electroless plating bath was formulated having the following ingredients.

To 1 liter of deionized water was added:

Grams Cobalt chloride Nickel chloride 40 Ammonium chloride 50 Sodium citrate 100 Sod um hypophosphite 30 The pH of the solution was adjusted to 9 with ammonia and the bath was heated with stirring to C. To the bath was added 1% by weight of the solids in the bath of chromium powder and a steel workpiece was then immersed in the bath and plated for a period of 1 hour. After 1 hour there resulted a coating having a thickness of 34.75 microns, the coating being uniformly gray and exhibiting good adhesion to the substrate such that the coating did not peel or separate from the substrate when subjected to the bend test; the coating further had the several desirable properties and characteristics described above with respect to the coating produced by the process of Example 1.

In each of Examples 1 through 22, above, the reducing agent utilized has been a hypophosphite. It will be understood that other suitable reducing agents may be used in the place thereof, preferred alternative reducing agents being alkyl-borazanes and borohydrides. Specific examples of suitable alkyl-borazanes are N-diethylborazane and dimethyl-borazane. An example of a suitable borohydride is sodium borohydride.

The following example illustrates yet another electroless plating metal and an electroless plating bath useful in carrying out the process of the present invention:

EXAMPLE 23 An electroless plating bath was formulated having the following ingredients:

Copper sulfate-l5 grams per liter.

Sodium hydroxide7.5 grams per liter.

Rochelle salt-7.5 grams per liter.

Formaldehyde solution (37% )-44 milliliters per liter. pH-12.5.

Temperature--25 C.

There was added to the electroless plating bath 1% by weight of the solids in the bath of chromium powder, maintained in suspension by mechanical agitation of the bath solution. A steel workpiece was immersed in the plating solution and plating was carried out for a period of 1 hour. After the 1 hour period, the workpiece carried an appreciable coating of copper thereon having dispersed uniformly therethrough chromium particles, the coating having the hardness and corrosion resistance as well as other desirable properties and characteristics discussed with respect to the coating produced by the process of Example 1.

The processes of this invention are also fundamentally independent of the physical shape of the metallic particles. Hence these particles may be in the form of fibers, powders, flakes, chips, turnings or any other such shapes. The following example illustrates the use of metallic particles in the form of flakes.

EXAMPLE 24 Ten grams of Type 304 stainless steel flakes containing about 18% chromium and 8% nickel, the balance being essentially iron with small amounts of manganese, silicon and carbon, were treated with ml. of concentrated nitric acid for one hour to clean and passivate the surface. The plating bath and process of Example 1 were again duplicated except that the flakes were substituted for the chromium powder. After one hour of plating time, there resulted on the surface of the steel workpiece a smooth, dull coating having a thickness of 15 microns. The physical and chemical properties of the coating produced compared favorably with coatings produced in the foregoing examples.

The following are yet other examples of workpieces which may be successfully coated utilizing the processes of the present invention, the chemical composition being other than the steel and aluminum given in the above specific examples.

EXAMPLE 25 The process of Example 19 was repeated using a workpiece consisting of magnesium with essentially the same results in regard to the hardness and corrosion resistance of the coating obtained therein.

EXAMPLE 26 The process of Example 1 was repeated using a workpiece consisting of copper with essentially the same results in regard to the hardness and corrosion resistance of the coating obtained therein.

EXAMPLE 27 The process of Example 1 was repeated using a workpiece consisting of nickel alloy with essentially the same results in regard to the hardness and corrosion resistance of the coating obtained therein.

EXAMPLE 28 The process of Example 1 was repeated using a workpiece consisting of beryllium alloy with essentially the same results in regard to the hardness and corrosion resistance of the coating obtained therein.

EXAMPLE 29 The process of Example 1 was repeated using a workpiece consisting of titanium alloy with essentially the same results in regard to the hardness and corrosion resistance of the coating obtained therein.

The various other methods for maintaining the metallic particles in suspension described previously herein may be substituted in the practice of the process described in Example 1 yielding similarly good results with respect to maintaining a good suspension of said metallic particles in the plating bath. For example, the steel workpiece in Example 1 may be slowly rotated while the bath solution is rapidly circulated throughout by means of a circulating pump resulting in a good suspension of the chromium particles in the bath solution.

From the above it will be seen that there have been provided processes for electroless metallizing of workpieces to provide thereon electroless plating metal coatings incorporating therein metallic particles, which processes fulfill all of the objects and advantages set forth above. In addition, the processes provide coated workpieces with the improved coatings thereon in accordance with the objects set forth. And finally, baths for the chemical plating of catalytic materials with an electroless plating metal coating incorporating therein metallic particles are provided which when utilized in accordance with the processes set forth will produce such coated workpieces.

While there have been described what are at present considered to be certain preferred embodiments of the invention it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A process of electroless metallizing a body to provide thereon a metal coating incorporating therein metallic particles, which process comprises contacting said body with an electroless metallizing bath consisting essentially of an aqueous solution of an electroless metal plating salt and a chemical reducing agent therefor and a quantity of metallic particles, said particles being selected from the group consisting of chromium, molybdenum, tungsten, boron, titanium, vanadium, zirconium, hafnium, niobium, tantalum, and alloys thereof, said particles being present in said bath in an amount by weight no greater than about ten times the weight of the electroless plating metal in said bath expressed as free metal, and maintaining said particles in suspension throughout said bath during the metallizing of said body, thereby to produce on the surface of said body a coating of the electroless plating metal having said metallic particles uniformly dispersed therethrough.

2. The process of electroless metallizing set forth in claim 1, wherein said metallic particles have dimensions in the range from about 0.1 micron to about 50 microns.

3. The process of electroless metallizing set forth in claim 1, wherein the coating of the metal produced on said body has a thickness in the range from about 1 micron to about 250 microns.

4. The process of electroless metallizing set forth in claim 1, wherein said particles are maintained in suspension throughout said bath by mechanically agitating said bath and said particles.

5. The process of electroless metallizing set forth in claim 1, wherein said particles are maintained in suspension throughout said bath by passing said bath with said particles therein past said body.

'6. The process of electroless metallizing set forth in claim 1, wherein said particles are maintained in suspension by streams of minute bubbles of gases passing through said bath.

7. The process of electroless metallizing set forth in claim 1, wherein said particles are maintained in suspension throughout said bath by agitation of said body within said bath.

8. The process of electroless metallizing set forth in claim 1, wherein said particles are maintained in suspension throughout said bath by slow rotation of said body in said bath in conjunction with rapid circulation of the bath solution with said particles past said body.

9. The process of electroless metallizing set forth in claim 1, wherein said particles are formed of a metal selected from chromium and alloys thereof.

10. The process of electroless metallizing set forth in claim 1, wherein said particles are formed of a metal selected from molybdenum and alloys thereof.

11. The process of electroless metallizing set forth in claim 1, wherein said particles are formed of a metal selected from tungsten and alloys thereof.

12. The process of electroless metallizing set forth in claim 1, wherein said particles comprise a mixture of first particles formed of a metal selected from chromium and alloys thereof and second particles formed of a metal selected from molybdenum and alloys thereof.

13. A process of coating a body with a nickel coating incorporating therein metallic particles, which process comprises contacting said body with a bath consisting essentially of an aqueous solution of a nickel salt and a reducing agent therefor and a quantity of metallic particles, wherein said particles are selected from the group consisting of chromium, molybdenum, tungsten, boron, titanium, vanadium, zirconium, hafnium, niobium, tantalum, and alloys thereof, said particles being present in said bath in an amount by weight no greater than about ten times the weight of the nickel in said bath expressed as nickel metal, and maintaining said particles in suspension throughout said bath during the coating of said body, thereby to produce on the surface of said body a coating of nickel having said metallic particles uniformly dispersed therethrough.

.14. The process of coating set forth in claim 13, wherein said particles are formed of a metal selected from chromium and alloys thereof.

15. The process of coating set forth in claim 13', wherein said particles are formed of a metal selected from molybdenum and alloys thereof.

16. The process of coating set forth in claim 13, wherein said particles are formed of a metal selected from tungsten and alloys thereof.

17. The process of coating set forth in claim 13, wherein said particles comprise a mixture of first particles formed of a metal selected from chromium and alloys thereof and second particles formed of a metal selected from molybdenum and alloys thereof.

18. The process of coating set forth in claim 13, wherein said reducing agent is a hypophosphite.

19. The process of coating set forth in claim 13, wherein said reducing agent is selected from alkyl-borazanes and borohydrides.

20. The process of coating set forth in claim 13, wherein the body is essentially formed of a material selected from iron, aluminum, magnesium, copper, nickel, titanium, beryllium, and alloys thereof.

21. A process of coating a body with a cobalt coating incorporating therein metallic particles, which process comprises contacting said body with a bath consisting essentially of an aqueous solution of a cobalt salt and a reducing agent therefor and a quantity of metallic particles, wherein said particles are selected from the group consisting of chromium, molybdenum, tungsten, boron, titanium, vanadium, zirconium, hafnium, niobium, tantalum, and alloys thereof, said particles being present in said bath in an amount by weight no greater than about ten times the weight of the cobalt in said bath expressed as cobalt metal, and maintaining said particles in suspension throughout said bath during the coating of said body, thereby to produce on the surface of said body a coating of cobalt having said metallic particles uniformly dispersed therethrough.

2.2. A process of coating a body with a copper coating incorporating therein metallic particles, which process comprises contacting said body with a bath consisting essentially of an aqueous solution of a copper salt and a reducing agent therefor and a quantity of metallic particles, wherein said particles are selected from the group consisting of chromium, molybdenum, tungsten, boron, titanium, vanadium, zirconium, hafnium, niobium, tantalum, and alloys thereof, said particles being present in said bath in an amount by weight no greater than about ten times the weight of the copper in said bath expressed as copper metal, and maintaining said particles in suspension throughout said bath during the coating of said body, thereby to produce on the surface of said body a coating of copper having said metallic particles uniformly dispersed therethrough.

23. The process of coating set forth in claim 22, wherein the reducing agent is formaldehyde.

24. A process of electroless metallizing a body to provide thereon a metal coating incorporating therein metallic particles, which process comprises contacting said body with an electroless metallizing bath consisting essentially of an aqueous solution of an electroless metal plating salt and a chemical reducing agent therefor and a quantity of metallic particles, said particles being selected from the group consisting of chromium, molybdenum, tungsten, boron, titanium, vanadium, zirconium, hafnium, niobium, tantalum and alloys thereof, said particles being present in said bath in an amount by weight no greater than about ten times the weight of the electroless plating metal in said bath expressed as free metal, maintaining said particles in suspension throughout said bath during the metallizing of said body, thereby to produce on the surface of said body a coating of the electroless plating metal having said metallic particles uniformly dispersed therethrough; and heating said coating to a temperature in the range from about 200 C. to about 1,300 C. for at least about one-quarter hour to bond said electroless plating metal coating and said metallic particles at the interfaces thereof.

25. The process of electroless metallizing set forth in claim 24, wherein said metallic particles have dimensions in the range from about 0.1 micron to about 50 microns.

26. The process of electroless metallizing set forth in claim 24, wherein the coating of the metal produced on said body has a thickness in the range from about 1 micron to about 250 microns.

27. The process of electroless metallizing set forth in claim 24, wherein said particles are formed of a metal selected from chromium and alloys thereof.

28. The process of electroless metallizing set forth in claim 24, wherein said particles are formed of a metal selected from molybdenum and alloys thereof.

29. The process of electroless metallizing set forth in claim 24, wherein said particles are formed of a metal selected from tungsten and alloys thereof.

30. The process of electroless metallizing set forth in claim 24, wherein said particles comprise a mixture of first particles formed of a metal selected from chromium and alloys thereof and second particles formed of a metal selected from molybdenum and alloys thereof.

31. The process of electroless metallizing set forth in claim 24, wherein heating said coating alloys said electroless metal coating and said metallic particles at least at the interfaces thereof.

32. A process of coating a body with a nickel coating incorporating therein metallic particles which process comprises contacting said body with a bath consisting essentially of an aqueous solution of a nickel salt and a reducing agent therefor and a quantity of metallic particles, wherein said metallic particles are selected from the group consisting of chromium, molybdenum, tungsten, boron, titanium, vanadium, zirconium, hafnium, niobium, tantalum, and alloys thereof, said particles being present in said bath in an amount by weight no greater than about ten times the weight of the nickel in said bath expressed as nickel metal, maintaining said particles in suspension throughout said bath during the coating of said body, thereby to produce on the surface of said body a coating of nickel having said metallic particles uniformly dispersed therethrough; and heating said coating to a temperature in the range from about 200 C. to about 1,300 C. for at least about one-quarter hour to bond said nickel coating and said metallic particles at the interfaces thereof.

33. The process of coating set forth in claim 32, wherein said particles are formed of a metal selected from chromium and alloys thereof.

34. The process of coating set forth in claim 33, wherein said coating is heated to a temperature in the range from 300 C. to about 800 C. for at least about onequarter hour to bond said nickel coating and said chromium particles at the interfaces thereof.

35. A process of coating a body with a cobalt coating incorporating therein metallic particles, which process comprises contacting said body with a bath consisting essentially of an aqueous solution of a cobalt salt and a reducing agent therefor and a quantity of metallic particles, wherein said particles are selected from the group consisting of chromium, molybdenum, tungsten, boron, titanium, vanadium, zirconium, hafnium, niobium, tantalum, and alloys thereof, said particles being present in said bath in an amount by weight no greater than about ten times the weight of the cobalt in said bath expressed as cobalt metal, and maintaining said particles in suspension throughout said bath during the coating of said body, thereby to produce on the surface of said body a coating of cobalt having said metalic particles uniformly dispersed therethrough; and heating said coating to a temperature in the range from about 200 C. to about l,300 C. for at least about one-quarter hour to bond said cobalt coating and said metallic particles at the interfaces thereof.

36. A process of coating a body with a copper coating incorporating therein metallic particles, which process comprises contacting said body with a bath consisting essentially of an aqueous solution of a copper salt and a reducing agent therefor and a quantity of metallic particles, wherein said particles are selected from the group consisting of chromium, molybdenum, tungsten, boron, titanium, vanadium, zirconium, hafnium, niobium, tantalum, and alloys thereof, said particles being present in said bath in an amount by weight no greater than about ten times the weight of the copper in said bath expressed as copper metal, and maintaining said particles in suspension throughout said bath during the coating of said body, thereby to produce on the surface of said body a coating of copper having said metallic particles uniformly dispersed therethrough; and heating said coating to a temperature in the range from about 200 C. to about 1,300 C. for at least about one-quarter hour to bond said copper coating and said metallic particles at the interfaces thereof.

References Cited UNITED STATES PATENTS 20 FOREIGN PATENTS 1,041,753 9/1966 Great Britain 117130(E) ALFRED L. LEAVITT, Primary Examiner 5 .T. R. BATTEN, JR., Assistant Examiner US. Cl. X.R. 

